If you don't get enough roughage in your diet, if you're constipated, or have irritable bowel syndrome (IBS), you may be taking a bulking agent like Metamucil, Citrucel, or Fiber-Con to make your stools larger and softer. If so, you may be pouring sugar or aspartame into your intestines.
 
Sugar feeds the bad bacteria that can lead to fermentation, gas, and a suppressed immune system. Aspartame is an artificial sweetener linked to so many health problems that it takes a book that's nearly 1,000 pages long to document all of them (Roberts, J.J. MD. Aspartame Disease: An Ignored Epidemic, Sunshine Sentinel Press, Inc., West Palm Beach, FL). You may need a bulking agent. But you don't need one with sugar or aspartame.
 
Psyllium comes from the Plantago ovata plant. Sometimes the seeds and husk are used as a bulking agent. Both are mucilaginous, which means that when you put them in water, they absorb a lot of water and form a gel, softening and increasing the size of solid wastes. Psyllium is particularly resistant to fermentation, so it's not likely to cause gas. It contains more fiber and it breaks down more slowly, producing large amounts of butyric acid. Butyric acid prevents the development of cancer cells and appears to protect against colon cancer. In one study, a group of colon cancer patients who took 20 grams of psyllium seed a day for three months had a 42 percent increase in their butyric acid levels.